Looks like their might be a harness option for the tc radio to add an amp. Maybe something like this can be combined with the tc radio to add our stock amp and keep all the speakers. I wonder if there is a cheaper DIY approach.

That tocoma radio looks promising. I am sort of interested in the scion one though just because of the charging capabilities of the ipod hook up, but this might be good enough for me and I can just run a power adapter.